POSTERIOR PART OF LOWER EXTREMITY. 377 



muscle above and below from the gemelli. (Fig. 259.) Cut the muscle near its 

 insertion into the greater trochanter, and then trace it back into the pelvis 

 through the lesser sacro-sciatic foramen. Notice the strong converging tendin- 

 ous bands on the under surface of the muscle. Also see the origins of the 

 gemelli from the ischial tuber and spine. (Fig. 226.) 



Reduced to its simplest terms, wliat is a rational pliysiological grouping of tlie 

 muscles primarily concerned in the movements of t lie 1 tip-joint? 



(i) Flexors of the thigh on the abdomen ; (2) extensors of the thigh on the 

 abdomen ; (3) adductors of the thigh on the pelvis ; (4) abductors of the thigh 

 on the pelvis ; (5) internal rotators of the thigh ; (6) external rotators of the 

 thigh. 



Xamc the flexor muscles of tlic tJiigh. 



The iliacus and psoas magnus, inserted into the lesser trochanter of the femur, 

 are, as Morris points out, almost pure flexor muscles. When, however, they 

 deviate from flexion, they are to some extent internal rotators, and not, as is 

 sometimes suggested, external rotators. Nerve-supply, second and third lumbar 

 nerves. 



Hoiv is tlie t/iig/i extended on the pelvis / 



By the action of the gluteus maximus, which is the direct antagonist of the 

 psoas and iliacus. Nerve-supply, the inferior gluteal nerve. 



Name the abductors of tJie hip-joint. 



The tensor vaginae femoris, the gluteus medius, the gluteus minimus. 

 Nerve-supply, superior gluteal. 



Name t/ie adductors of the t/iigh or hip-joint / 



The obturator externus, the adductor longus, the adductor brevis, the adduc- 

 tor magnus, and the adductor gracilis. Nerve-supply, the obturator. 



How is tJie t/iig/t or /tip-joint rotated inward ? 



By the anterior segments of the members of the abductor group of muscles 

 viz., the glutei minimus and medius and the tensor vaginae femoris ; and, in addition, 

 according to Morris, by the ilio-psoas muscle. Nerve-supply, superior gluteal. 



Name the muscles that rotate the thigh outward. 



The pyriformis, the obturator internus, the two gemelli muscles, and 

 the quadratus femoris. These muscles all derive their nerve-supply from the 

 sacral plexus. The obturator externus, although strictly speaking an adductor 

 muscle, becomes an external rotator when the patient is in the sitting posture. 



Now, on figure 263 study the relation of the quadratus femoris, obturator 

 internus, and the gemelli to each other. On figure 262, on which the quadratus 

 and gemelli are removed, study the relation of the obturators to each other. 



BACK PART OF THE LEG. 



Locate the fibrous arch connecting the heads of the gastrocnemius muscle. 

 (Fig. 259.) Notice passing downward into the deep intermuscular space the 

 popliteal artery and vein, in their proper relation to each other, and the internal 

 popliteal nerve. (Fig. 264.) Carefully isolate these structures from each other 

 and from the arch. Then lift the arch upward and cut down between the two 

 heads of the gastrocnemius to the point where this muscle joins the soleus. Also 

 notice between these two muscles the plantaris, with its very long tendon. (Fig. 

 264.) Now cut the gastrocnemius (Fig. 264), and trace each head across the 

 joint to its exact origin on the femur. (Fig. 227.) Notice the difference in origin 

 25 



